The present invention relates to devices and methods for stabilizing vertebral bodies. More particularly, it relates to devices, systems and methods for stabilizing vertebral bodies with curable material or other stabilizing structures.
Surgical intervention at damaged or compromised bone sites has proven highly beneficial for patients, for example patients with back pain associated with vertebral damage. During certain bone procedures, cancellous bone within a vertebral body is supplemented by an injection of a palliative (or curative) material employed to stabilize the trabeculae. For example, superior and inferior vertebrae in the spine can be beneficially stabilized by the injection of an appropriate, curable material (e.g., PMMA or other bone cement). In other procedures, percutaneous injection of stabilization material into vertebral compression fractures by, for example, transpedicular or parapedicular approaches, has proven beneficial in relieving pain and stabilizing damaged bone sites. Other skeletal bones (e.g., the femur) can be treated in a similar fashion. In any regard, bone in general, and cancellous bone in particular, can be strengthened and stabilized by a palliative injection of bone-compatible material.
The conventional technique for stabilizing a damaged vertebral body includes accessing the interior of the vertebral body according to known techniques and delivering curable material to the interior of the vertebral body in a cloud-like formation. The convention technique presents several shortcomings. The cloud-like formation creates a somewhat spherical hardened structure within the vertebral body that provides gradations of support to the endplates of the vertebral body. The cloud-like formation may only provide support at a point or a relatively small portion of an endplate. Because the cloud-like formation does not distribute force broadly over the surface of an endplate, pressure points within the vertebral body may result. This may cause fracture and/or refracture of the endplate of the vertebral body. As a result, the local structure of the vertebral body may not be optimally stabilized.
Another shortcoming of the conventional technique is that it fails to restore a fractured vertebral body to the height of the vertebral body prior to fracture. A normal vertebral body contains two substantially planar endplates that are substantially parallel to each other. In an osteoporotic or otherwise damaged or diseased vertebral body, an endplate, or a region adjacent an endplate, fractures causing the endplates to no longer be substantially planer. The “height” between the endplates is reduced in at least a portion of the vertebral body. After a fracture, a new load condition on the back occurs. A person may accommodate the fractured state and associated pain by realigning the back through hunching or bending over. Once the fracture occurs the person will thus continue to bend over to minimize pain associated with the fracture.
A conventional vertebroplasty fails to adequately restore the lost height of the fractured vertebral body to the normal pre-fractured state. According to one known method, height restoration of the vertebral body is a purported benefit of Kyphoplasty. Kyphoplasty is a modification of vertebroplasty in which an expandable balloon is used to create a cavity in the central portion of a vertebral body before the injection of cement. In a Kyphoplasty, the expanding of the balloon within the vertebral body is said to increase the height of the vertebral body in an effort to restore it to its pre-fractured state. It has been observed that the balloon creates a cavity surrounded by a region of collapsed marrow within the vertebral body. This cavity is then filled with curable material after the balloon is removed. Although the Kyphoplasty procedure purports to restore vertebral body height, the generally spherical curable material deposit also provides only gradations of support to the endplates of the vertebral body in a manner similar to the cloud-like formation of a vertebroplasty procedure.
Another shortcoming of known methods of stabilizing a vertebral body are the effect the curative methods for a fractured vertebral body have on adjacent diseased and weakened vertebral bodies. Because the known methods create gradations of support within the vertebral body, only points or small portions of the endplates of the vertebral body are stiffened and stabilized. Localized regions of stiffness within a vertebral body create pressure points on adjacent vertebral bodies. Where those adjacent vertebral bodies are diseased or weakened, the localized regions of pressure can cause fractures in the adjacent vertebral bodies.
Additionally, in cases where an endplate of a vertebral body may be stabilized by curable material, but height has not been restored, adjacent vertebral bodies must compensate for the stiff, but misaligned vertebral body. This too may cause fractures in adjacent diseased or weak vertebral bodies.
It is also known that common curable materials intended to provide structural integrity to a damaged vertebral body, such as polymethylmethacrylate (PMMA) bone cement, possesses a level of toxicity to the body. It is preferable to minimize the use of such materials in the body to the extent possible. Non-toxic materials that may be injected into a vertebral body, such as, hydroxyapatite, calcium phosphate, antibiotics, proteins, etc., promote bone growth within the vertebral body. Such materials by themselves, however, do not generally provide enough structural integrity to an injection site on their own.
As a result, there exists a need to create a structure within the vertebral body to more fully stabilize the endplates of the vertebral body and distribute force more broadly across an endplate. The stabilization of the endplates may also be used in conjunction with methods to restore height to the vertebral body. There also exists a need to minimize the use of PMMA in the vertebral body. There also exists a need to provide patients better comfort during the procedure.